I accessed my SVN repository (http://) using TortoiseSVN via a proxy server and tried to commit some changes.

Solution:

I disabled the proxy server in Tortoise SVN’s Settings. i.e. I did NOT use a proxy server to access my SVN repository.

Note: If you must use a proxy server, you may fix this problem by installing certificates and accessing your SVN repository via HTTPS.

Root Cause:

TortoiseSVN uses WebDAV to access an SVN repository. Proxy servers which are not compliant with WebDAV will strip off HTTP headers containing WebDAV methods such as MKACTIVITY. However, if you access the SVN repository via HTTPS and a proxy, the proxy server will not inspect the request and will forward it as is.

NOTE:

(1) The solution above describes a successful problem-solving experience and may not be applicable to other problems with similar symptoms.

(2) Your rating of this post will be much appreciated. Also, feel free to leave comments.